Pyrolytic treatment of hydrocarbons



June l, 1937. P. c. KEITH. JR

PYHOLYTIC TREATMENT 0F HYDROCARBONS Filed Feb. 1, 1933 www INVENToR- PE/Pc YcKf/TH, JF.

ATTORNEY- UNITED sTATEs PATENT ori-ICE PYROLYTIC TREATMENT F HYDROCAR- BONS Percy c. Keith, Jr., Port washington, N; Y., as-

signor to Gasoline Products Company, Inc., Newark, N. J., a corporation of Delaware e Application February 1, v1933, sei-iai No. 654,613

3 claims. (ci. 19e-9) My invention relates to the pyrolytic treatment or conversion of hydrocarbons and the recovery of valuable products therefrom.

In the pyrolytic decomposition or cracking of hydrocarbons, and more particularly petroleum oils, the primary products are lower boiling liquids such as gasoline or other normally liquid materials of relatively high volatility, normally gaseous hydrocarbons including ilxed gases, and relatively high boiling hydrocarbons varying from gas oil to heavy tars approaching coke in character. The value of these gases' and liquids is relatively low as comparedwith motor fuels such as gasoline and theinterm'ediate products, but these materials represent potential sources of valuable materials such as normally liquid hydrocarbons either aromatic in characteror resembling aromatics in having desirable antiknock properties when used as motor fuel.

My invention therefore has for objects the production of hydrocarbon liquids from normally gaseous hydrocarbons and from relatively high. -boiling hydrocarbon materials and, in on'e aspect at least, reduction of the amounts of gases and tarry .materialproduced in plants for cracking petroleum oils.

My invention has for further objects such additional specific operating advantages and results as may hereinafter be found to obtain.

My invention contemplates the contacting of low-boiling or normally gaseous hydrocarbons with relatively high-boiling' hydrocarbons, such as heavy, substantially non-volatilizable or tarry material derivedfrom pyrolytic decomposition of hydrocarbon materials such as petroleum oils and coal, under such conditions that unsaturated hydrocarbon constituents, such for example as oleilns, are polymerized or otherwise converted to.

heavier or lighter products by inter-reaction between the low-boiling or gaseous hydrocarbonsV and the tarry material.

This inter-reaction is carried out under such conditions that it results in the formation of valuable productsof normally liquid character, more or less intermediate between the gaseous material and the heavier material and capable of separation in a form suitable for use as motor fuel or for admixture-with motor fuel or capable of conversion by pyrolytic decomposition, that is to say, either by cracking or straight distillation, to produce motor fuel or material advantageousiy employed for admixture with gasoline or other motor fuel to increase the antiknock character of the latter.

In general, the normally gaseous hydrocarbon materials which I prefer to employ are those containing substantial proportions of unsaturates, that is to say,4 not less than and preferably 25% or more, of unsaturates such as olens.

I may, however, employ, as a source of such gases,v gases containing hydrocarbons of thev paraflln" series, preferably ethane, propane and butane. Methane,l being more stable, is less desirable, although it may be employed under suitable conditions and is, as a matter of fact, present in many gases which it may be desirable to employ in my process.

Thus I may initially employ natural gas, especially that which contains substantial amounts lof ethane, prop ne and butane, or gaseous products resulting from the decomposition of hydrocarbon materials such as hydrocarbon oil and coal More speciilcally, I may employ substantially "dry gases resulting from the more or less drastic cracking of petroleum oil, or mixtures of liqueiiable materials, such for example as .stabilizer reux containing considerable amounts of butane and pentane.

' Such gaseous hydrocarbons are preferably'flrst l subjected to pyrolytic conversion or cracking to promote the formation of unsaturates such as oleiins, capable of polymerization or conversion to hydrocarbons of a .normally liquid character. However, such conversion or cracking may be dispensed with when gases containing substantial proportions of olens and other unsaturates are'employed, for example, those gases produced in relatively hlghtemperature oil-cracking operations such as vapor-phase operations conducted at temperatures of the order of V1000 F. or higher. l

The relatively high-boiling hydrocarbons which I employ in my process are preferably those which contain substantial amounts of unsaturated hydrocarbon constituents. Thus, I may employlcertain cycle stocks or gas oils rich in unsaturates. I prefer, however, to employ so-called pressure tars produced in the pyrolytlc decomposition of petroleum oil, for example, a nal tar from the ash tower of a cracking plant, which tar has been separated from relatively light constitutents, or a lighter tar or residuum from the high-pressure distillation zone or evaporator of a cracking plant, which tar contains considerable amounts oi relatively light constituents. While I prefer to employ oils producedin the destructive decomposition of petroleum oils, I may or very low boiling hydrocarbons initially to pyrolytic conversion or cracking for the purpose of producing or increasing the proportion of polymerizable unsaturated hydrocarbons and` then to lead the products, preferably after removal of any normally liquid constituents therefrom, into a separate polymerization and reaction stage, the initial pyrolytic conversion and the polymerization or reaction in the presence of the heavier material may take place together or may to some extent overlap.

Where, however, the initial pyrolytic couver--V sion stage is performed separately from the subsequent polymerization and reaction stage, I pre- -fer to so limit the time element in the pyrolysis stage as to make it possible to carry out in the reaction stage, in contact with the heavier material, as much as possible of the polymerization of the unstable materials resulting from the initial pyrolytic conversion.

The polymerization of the unstable or unsaturated products resulting from the initial pyrolytic conversion of the normally gaseous or low boiling hydrocarbons or present as such in the gaseous material and the reaction between the polymerized or unpolymerized products and the heavier material or constituents thereof, is carried out under such elevated pressure and temperature as to promote polymerization of unsaturates such as olei'lns. The products of reaction from the polymerization and reaction stage are removed and fractionated to effect the separation therefrom of normally liquid products and normally gaseous products.

All or a portion of the lighter liquid products from the polymerization and reaction stage may then, if unsuitable for use directly as motor fuel or for direct addition tc motor fuel, such as gasolina-be subjected to distillation or cracking to further refine the same, aad to produce motor fuel or material adapted to be combined with motor fuel and having the property of in the materials themselves andthe results desired.

Ordinarily, however, I employ in the polymerizationand reaction stage temperatures of from 600= to 1250 F., preferably temperatures below those .at which active coke formation takes place, for example, temperatures of from 700 to 900 F., and pressures of from '750 to 3000 pounds per square inch and preferably from 1000 to 2000 poundsA per square inch. In the initial gas pyrolysis stage, the pressures employed are preferably much lower, but may be similar to those employed in the subsequent polymerization and reaction stage, while highertemperatures are preferred, for example; temperatures of from 1100 to l750 F. The temperatures maintained in the gas pyrolysis stage may, however, be reduced by the employment of suitable catalysts.

The pressures employed in the two stages may be made equal or substantially equal to avoid the difliculty of increasing the pressure upon the highly heated materials between the two stages, but it is possible according to my invention to employ lower pressures in the pyrolytic conversion stage than are employed in the subsequent polymerization and reaction stage without mechanical difficulty. For example, the pressure maintained in the pyrolytic conversion stage may be from substantially atmospheric to about pounds per 'square inch, whereas the pressure maintained in the polymerization and reaction stage may be from 1000 pounds to 3000 pounds per square inch, it being understood that the polymerization and reaction are favored by high pressures which may not be necessaryn the preliminary conversion stage.

Where desired, catalysts may be employed in either or both of the aforesaid stages. Such catalysts may comprise those ordinarily used in the pyrolysis of hydrocarbons, as, for example,

` metallic halides such as aluminum chloride and zinc chloride, and in the polymerization and reaction stage may alternatively comprise such known catalysts as are commonly employed in hydrogenation processes, for example, activated carbon, fullers earth, oxides of chromium, nickel and cobalt, and oxides and salts of vanadium and molybdenum, and copper.

In the drawing accompanying and forming a part of this specification, the single figure is intended to represent more or less diagrammatically a preferred form and manner in whichmy Ainvention may be embodied and practiced.

Referring to this drawing, a hydrocarbon gas,

such for example as dry gas obtained in the pyrolysis of .petroleum oil, is drawn from a source I and is delivered through a conduit 2 at high pressure bymeans of a pump 3 to a-heating coil 4 situated in a furnace 5 of suitable character.

The hydrocarbons passing through the coil 4 are preferably subjected to a temperature of from 1500 to 1600 F. and a limited pressure of for example up to 200 pounds per square inch, and

tarry hydrocarbon material introduced from a suitable source (not shown) througha conduit l by means of a pump 8.

By thus quenching the products of conversion from the coil 4, the extent of pyrolytic conversion initiated in the coil 4 may be controlled, and compression of the commingled materials is facilitated. In this instance,` the relatively cool commingled gases and tar are delivered by means of a pump 9 to a polymerizing or reaction coil I0 located in a suitable furnace structure Il, where they are brought to the reaction temperature of from 600 to' 1250 F., under a pressure of from 750 to 3000 pounds per square inch.

During the passage of the commingled hydrocarbon materials through the reactionV coil I0, the unstable unsaturated products resulting from the pyrolytic conversion of the normally gaseous or low-boiling hydrocarbons are polymerized orotherwise converted to materials of higher boiling points, whereas by reaction of these materials with constituents of the tarry hydrocarbon material the latter are converted into materials of dif-V ferent character from the original constituents of the tar. The ultimate result of this polymerizaion and inter-reaction is the 'formation of increased quantities of normally liquid hydrocarbons having boiling points intermediate between those of the principal constituents of the original gaseous or low-boiling hydrocarbons and the tarry hydrocarbons, and a consequent reduction -in the amounts of normally gaseous hydrocarbons and heavy or tarry hydrocarbons ultimately yielded.

The products of reaction pass from the-reaction coil lil through a conduit l2 having a reducing valve I3 to a low-pressure flash tower or fractionating tower Il, where they.- are separated into `vapors and liquids under the -reduced pressure and temperature at which the flash tower is maintained. The flash tower Il may be provided with an upper fractionatingsection Illa where, by suitably cooling or reiiuxing the vapors, an intermediate fraction may be recovered, this fraction being withdrawn through a conduit Mb.

The uncondensed vapors pass oil from the fractionator Ma through a vapor conduit I5 to a suitable condenser IB and separator I'l. The normally liquid light hydrocarbon products condensed in the separator l1 are withdrawn through an outlet i8 while the uncondensed gases pass olf through a conduit i9 either to be used as fuel version stage as desired. In the former instance these gases may be withdrawn through an outlet 2i having a valve 22, whereas in the latter instance they may be deliveredby means oi a conduit 23 having a valve 2t to the conduit 2 at a point ahead of the pump 3.

The tar or other liquid fraction separated in the dash tower it is withdrawn through a conduit 25 having a valve 2t or all or any portion of it y be returned to the reaction coil le by means of a pump 2 through a conduit 23 havingl a valve en the conditions of pressure and temperature to which the hydrocarbonsare subjected in l vthe coil d are such that normally liquid materials are present in substantial `amount in the gases leaving the coil 4,1 may remove vthese liquid materials prior to commingling the products from the coil 4 with tarry material. y For this purpose I provide a valve 32 located in the conduit 6 and a branch conduit 33 having a valve 34.

With the valve 32 closed and the valve 34 open,

the products coming from the coil I pass through a heat exchanger l5, where they are partially cooled, and into a cooler 38, where normally liquid constituents are condensed. The condensate collects in a separator 3l, from whichit'is withdrawn through aconduit 38, while the uncondensed gases pass through a conduit 39l to a pump Y 40, where they are raised to a. pressure at least equal to that obtaining in the reaction coil l0. The compressed gases then pass through al conduit-4i, the heat exchanger I5, a conduit 42, a heating coil t3, and conduits 4I and 8 to the lcoil ill. In this instance the pump 8 may be bypassed through a line 50 provided for that purpose, by closing a valve 6a in the conduit i and opening a valve 50a inV the Vconduit 50. When this is done, the tarry material may also be preheated prior to commingling it with the products of conversion from the coil 4.

The coil t3 is, when used at all. ordinarily employed simply as a preheater, although, if desired,- the temperature at this point may be made high enough to eilect some cracking or conversion of the gases.

' `the latter, although it may be subjected to further treatment if desired.

VThe fraction recovered at Mb will ordinarily comprise heavier hydrocarbon oil, and may be subjected to distillation or pyrolytic decomposition to recover therefrom a motor fuel or an oil suitable for blendingwith motor fuel, while the still heavier residual oil or tar removed at 26 may be withdrawn from the system or recycled as set forth hereinabove. If the gaseous materials employed in the operation already contain the necessary or desired unsaturates, such as oleflns, the coil I may be employed mainly in the capacity of a preheater for raising the gases to the desired temperature prior to their introduction into the reaction coil I0. Such gaseous materials may, of course, in-

clude those gases produced during relatively high temperature oil cracking or naphtha reforming operations, or gases derived from the cracking or conversion of any hydrocarbon materials including natural gas, refinery gas. casinghead gas, and the like.

Moreover, the conversion of saturated hydrocarbons to unsaturated hydrocarbons may be caused to take place more or less simultaneously with the polymerization and inter-reaction, that is to say, in the presence of the tarry material, especially where the temperatures maintained in the `coil in are relatively high. In this instance, the temperature maintained in the coil lil may be as high as from 1500 to about 175i)o F.

While in the specific instance illustrated in the drawing, the polymerizing and reaction stage is shown as taking place in a pipe coil; such a coil may be followed or replaced by an enlarged chamber or vessel, which may be insulated where so desired. The choice of apparatus at this point will of course depend upon the temperatures to be maintained and the temperatures of the prOducts about to be treated, as well as the time factor.\ Since the polymerization reaction is exothermic in character, in instances where the' polymerization reaction takes place-vigorously, thecoil I Il may be provided with means for removing excess heat developed in the reaction. Thus I may supply the coil I0 externally with a cooling fluid, as for example by spraying water over the coils ill or. by immersing the coil l0 in a bath of water, oil or other cooling iiuid, or by passing cool gas around the coil Ill.

It will be obvious tov those skilled in the art that my invention is susceptible of considerable modication in detail, and is therefore not lim-` products, cooling the gaseous products to remove therefrom liquid products formed during said pyrolytic conversion, intimately contacting gaseous products resulting from said conversion ture while being maintained under superatmospheric pressure for a sumcient period of time to effect the formation of normally liquid low boiling hydrocarbon oil and fractionating the resultant products to recover said low boiling hydrocarbon oil in liquid form.

2. The process which comprises subjecting normally gaseous hydrocarbons-of the parafn series substantially free from normally liquid hydrocarbon oil to a temperature of from 1,100" to 1,750 F. to eiect a pyrolytic conversion of such hydrocarbons to olenic hydrocarbons and liquid products, cooling the gaseous products to remove therefrom liquid products formed during said pyrolytic conversion, compressing the remaining gaseous products to a pressure of at least 750 pounds per square inch, intimately contacting the gaseous products with normally liquid residual oil obtained in the pyrolytic decomposition of hydrocarbons, reacting the gaseous products while under pressure and at a temperature of from 600 to 1,250 F. with said residual oil obtained in the pyrolytic decomposition of hydrocarbons prior to the separation of any heavy oil therefrom and in the absence of added catalyst for a sufficient period of time to eiect the formation of normally liquid low-boiling hydrocarbon oil, and fractionating the resultant products to recover said low-boiling hydrocarbon oil in liquid form.

during said pyrolytic conversiom compressing the gases to a high superatmospheric pressure in excess of that obtaining in the pyrolytic conversion zone, passing the compressed gases through said heat exchange zone t'o heat the same, intimately contacting the gaseous products with normally liquid residual oil obtained n` the pyrolytic decomposition of hydrocarbons, further heating the compressed gases and said oil to a temperature of from 600 to 1,250 F. prior to the separation of any heavy oil therefrom and in the absence of added catalyst, maintaining them at this temperature and under such pressure in the presence of said residual oil obtained in the pyrolytic decomposition of hydrocarbons for a suilcient period of time to eiect the formation of normally liquid low-boiling hydrocarbon oil, and fractionating the resultant products to recover said low-boiling hydrocarbon oil in liquid form.

PERCY C. KEITH, Ja. 

